The superconducting density of states at zero field of 2H-NbSe\(_{1.8}\) S\(_{0.2}\)  shows a smooth distribution of gap values[1]}. It is useful to compare the effect of S substitution with the application of pressure in 2H-NbSe\(_2\)[2]}, [3]}. Pressure increases T\(_c\)  up to 8.5 K at 10GPa, and then T\(_c\)  is slightly reduced to 7.5 K at 20 GPa. S substitution by contrast decreases T\(_c\)[4]}. As shown in Ref. [1]}, the charge density wave (CDW) of 2H-NbSe\(_2\) , becomes strongly affected by S substitution in 2H-NbSe\(_{1.8}\) S\(_{0.2}\) . In Fig. REF a,b we compare topographic STM images of 2H-NbSe\(_2\)  with 2H-NbSe\(_{1.8}\) S\(_{0.2}\) . 2H-NbSe\(_2\)  shows CDW order with periodic modulations three times the in-plane lattice constant. In 2H-NbSe\(_{1.8}\) S\(_{0.2}\)  we also find CDW order at the same wavevector than for \(x=0\) . However, the intensity of the CDW modulation strongly varies with position, producing a disordered CDW pattern. Thus, the S substitution in 2H-NbSe\(_{1.8}\) S\(_{0.2}\)  leads to a superconductor which is very similar to 2H-NbSe\(_2\) , but in-plane isotropic. The mean free path estimated from the residual resistivity is of about \(\ell \approx \)  20 nm in 2H-NbSe\(_{1.8}\) S\(_{0.2}\) , significantly below \(\ell \approx \)  120 nm in 2H-NbSe\(_2\) . However, CdGM bound states are well identified in the LDOS[1]}.
